Compressor HVAC: Description and Operation

CIRCUIT OPERATION
The Compressor for the Air Conditioning System is driven by the engine by means of a belt drive and the A/C Compressor Clutch. The Clutch allows the Compressor to be disengaged when Air Conditioning is not required.

Operation of the Compressor depends on the particular A/C Mode selected at the Heater and A/C Controller. When the Ignition Switch is in RUN, battery voltage is supplied through the A/C HTR Fuse to the coil and contacts of the A/C Clutch Relay. With A/C ON selected, Terminal 1651 of the Heater and A/C Controller is grounded which energizes the A/C Clutch Relay. The contacts of the Relay close and battery voltage is supplied through the closed contacts and the normally closed A/C Accumulator Switch to the coil of the A/C Compressor Clutch. The coil is energized and the A/C Compressor Clutch engages.

If the refrigerant pressure drops to a point which may cause icing of the evaporator, the A/C Accumulator Switch opens, de-energizing the A/C Compressor Clutch.

When the refrigerant pressure rises to a point where cooling is required again, the A/C Accumulator Switch closes to re-energize the A/C Compressor Clutch.

The A/C Compressor Clutch Diode is connected across the terminals of the A/C Compressor Clutch.

Whenever the clutch is de-energized, the magnetic field around it collapses, generating an induced voltage in the clutch coil. The Diode provides a path for the current resulting from the induced voltage so that other circuit components are not damaged.